Process of purifying and dewaxing mineral oil



Patented July 2, 1935 UNITED-STATES; PATENT] OFFICE V j 2,006,816} j p a PRocEss OF PURIFYI NGAND DEWAXING MINERAL OIL George J. Strezynski, Poughkeepsiey N. Y., and 'WalterKronasser, -Graz,'Austria, assignors to The De Laval Separator Company, New York,

N. Y., a corporation of New Jersey 7 I Application oct b r'zs, 1933, Serial ro/694,760 4 Claims. (01. st rs) One of the steps in the production of high previously chilledoil. With the diluted chilled grade lubricating oils is treatment with concenoil is then mixed an acid, such asconcentrated trated sulfuric acid to remove undesirable consulfuric acid. The acid may be, however, less stituents which, if left, cause dark color in the preferably, added beforaorat the same time that,

, 5 oil and are liableto break down in use. the diluent isa-dded; 1 Themixed oil and diluent, ;,5

In order to reduce darkening of the color of or the mixed oil, acid and diluent, mayor may the oils this-treatmentis sometimes carried on notbe still further chilled; The mixtureis then at such lowtemperaturesthat solid-waxes are subjected to centrifugal force and the acidthrown out of solution. I 71 formed sludge and wax thereby separated from time of the methods for removal from the oil the oil, which is substantially wax-free. 1Q

of the sludges formed by .acid treatment is by In the above process, rapid chilling of the oil centrifuging. I 3 w at high viscosity with agitation will notcause When this. method is used on oils containing the ;-wax to separate in particles too small for wax it is difiicultand often impossible to obtain separation in the final step. On thecontrary, the

5 continuous discharge of the sludge because of particles of sludge contact with the smaller wax separation of wax in an independent layer beparticles and, when separated out by centrifugal tween the sludge and the oil, resulting in plugforce or even by gravity, carry the wax particles ging of the bowl. along into the same mass as the sludge. Appar- One object of our invention is to provide a ently the small particles of wax act as nuclei process by which such treatment and separation about which the sludge gathers, forming larger 20 can be accomplished without plugging. particles, each of which behave as a unit in the Another step in the refinement of many oils centrifuge, so that, as above stated, the wax and is the removal of waxes that make the oils vissludge are thrown out as one mass. It is possible, cous or even solid at the temperatures at which but not advisable, to carry on the process by addit is desired to use them. ing a small part of the diluent before the first 25 The most used methods for removal of wax described chilling, but the degree of dilution must are chilling to throw the wax out of solution not approximate that effected at a later stage of and gravity settling or centrifugal separation the process. By having the diluent colder than of the wax from the oil. the chilled wax-bearing oil, the rise in tempera- In all previously known methods it has been ture due to the acid reaction may be counter- 30 necessary to greatly dilute the oil and to chill acted, the latter action also being counteracted it very slowly with slow agitation in order to 'by further cooling the diluted oil prior to cenproduce wax particles that are large enough to trifugal separation. As the reaction between be moved by gravity or centrifugal force. If the acid and oil constituents is very slow at extremely oil is chilled qu c y, i5 C d at g viscosity low temperatures, it is sometimes advisable to 35 (Without d ut o 0 is a d While Chilling, only partially chill the oil before the acid treatthe wax will separate in particles too small for ment and fini h the chilling to the temperature separation any prevwusly knowgmethodsneeded to obtain the desired cold test of the oil We have discovered that it 1s possible to treat after the acid has completed its action.

40 mineral o1l contalnlng wax as to effect, by one Whether the on is subjected to one or a senes of Operations both de'waxmg acid rality of chilling operations, the temperature to purification. Our process comprises, in its preferred embodiment, the following series of steps. Whlch It Should be chlned before centnfugmg The oil, which may be a lubricating oil (either a Should be comparatlvfaly namely Varying distillate or a residuum) or a crude oil, without from 450 to substantlauY below 00 dependent 45 substantial dilution or reduction of viscosity, is on the Character of the 011 and also 011 the Cold rapidly chilled with violent agitation. To the test desired In the case of some p ional chilled oil is then added naphtha or some other Oils, h minimum temperature qui d f r both diluent which it is known to add to oil to change p fi i n nd W s y be as h h as 45 its viscosity and cause the oil and wax to have F. When the oil is chilled in stages, with acid 50 substantially different specific gravities and allow treatment following the first chilling stage and the particles to move freely through the liquid, centrifugal separation following the last chilling, such diluent having been previously chilled to a the initial chilling need not be below 45 F., but temperature not substantially above, and prefermay be lower, while the temperature of the last ably substantially below, the temperature of the chilling may not be below 35 Fpin the case of acid 'from a tank I}.

ters Patent is:

exceptional oils, but will ordinarily be below 10 F.

The drawing is a diagram of a dewaxing plant adapted'to practice my-improved process.

From a tank I [containing waxy oil, the' oil flows into a'tank Ii containing an agitator'driven by a motor lz'and surrounded by a jacket [3 chilled by coldbrlne or other refrigerating fluid froma pipe M. From a tank IS a diluent flows through a coil'within a tank It in which the diluent is chilled to a temperature not suntan? tially above, andlpreferably to a temperature somewhat below, thetempetature of the 'oil and w'ax flowing from the chilling and agitating tank a H. "The chilledrand agi oil andwax and the chilled diluent flow into a mixing and re action tank I8, into which also flows mineral The mixture of oil, wax, diluent and acid in tank l8 may be further (billed by means oi a coil 19 through; which flows cold brine or other" refrigerating fluid. From tank" the chilled mlxture'iio'ws into a centrifuge I, wherein the oil together with the diluent, or

most. of it, is, separated from the acid sludge and wax and any diluent which is notcarried of! withthe-oil. a v g What we claim and desire to protect by Lety 1. In the process of dewaxing mineral oil by chilling, addition of a diluent and a mineral acid, and centrifugal'separationof theoil from the acid-Ionned'sludge, the preliminary step 01 chilling the oil with'violent agitation before addition H: of the major part of the diluent, whereby the wax is conditioned to so coalescewith the sludge so as to facilitate its separation from the-oil.v

2. In the process of treating mineral oil containing wax to purify it and remove wax therefrom, rapidly chilling the oil with violent agitation, chilling a diluent to a temperature not substantially above that of tin ehilbd oil and addin the chilled diluent and a mineral acid to, and mixing them with, the chilled oil and wax, and

separating the acid-formed sludge and wax from the oil. a

3. The processor treating wax-bearing mineral oilto purify it and remove wax therefrom which comprises subjecting the oil to rapid chillin; without substantial dilution to'reduce its viscosity and to rigorous agitation, then adding a diluentadapted to: reduce the viscosity of the oil and at atemperature not substantially above that of the chilled Oil andalso mixing with the chilled oil [a mineral acid chilling the diluted and acid-treated oll be-runner redllte its tem and wax Irom liheoil.

mature, and separating thelacld-forrned sludge In the process of treating oil eon- 'taining wax to purify it and remove wax there 

